revisions API: have release_revisions() release "mailmap"

Extend the the release_revisions() function so that it frees the
"mailmap" in the "struct rev_info".

The log family of functions now calls the clear_mailmap() function
added in fa8afd18e5a (revisions API: provide and use a
release_revisions(), 2021-09-19), allowing us to whitelist some tests
with "TEST_PASSES_SANITIZE_LEAK=true".

Unfortunately having a pointer to a mailmap in "struct rev_info"
instead of an embedded member that we "own" get a bit messy, as can be
seen in the change to builtin/commit.c.

When we free() this data we won't be able to tell apart a pointer to a
"mailmap" on the heap from one on the stack. As seen in
ea57bc0d41b (log: add --use-mailmap option, 2013-01-05) the "log"
family allocates it on the heap, but in the find_author_by_nickname()
code added in ea16794e430 (commit: search author pattern against
mailmap, 2013-08-23) we allocated it on the stack instead.

Ideally we'd simply change that member to a "struct string_list
mailmap" and never free() the "mailmap" itself, but that would be a
much larger change to the revisions API.

We have code that needs to hand an existing "mailmap" to a "struct
rev_info", while we could change all of that, let's not go there
now.

The complexity isn't in the ownership of the "mailmap" per-se, but
that various things assume a "rev_info.mailmap == NULL" means "doesn't
want mailmap", if we changed that to an init'd "struct string_list
we'd need to carefully refactor things to change those assumptions.

Let's instead always free() it, and simply declare that if you add
such a "mailmap" it must be allocated on the heap. Any modern libc
will correctly panic if we free() a stack variable, so this should be
safe going forward.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 3 deletions

diff --git a/builtin/commit.c b/builtin/commit.c
index c7eda9bbb7..cd6cebcf8c 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1100,7 +1100,6 @@ static const char *find_author_by_nickname(const char *name)
 	struct rev_info revs;
 	struct commit *commit;
 	struct strbuf buf = STRBUF_INIT;
-	struct string_list mailmap = STRING_LIST_INIT_NODUP;
 	const char *av[20];
 	int ac = 0;
 
@@ -1111,7 +1110,8 @@ static const char *find_author_by_nickname(const char *name)
 	av[++ac] = buf.buf;
 	av[++ac] = NULL;
 	setup_revisions(ac, av, &revs, NULL);
-	revs.mailmap = &mailmap;
+	revs.mailmap = xmalloc(sizeof(struct string_list));
+	string_list_init_nodup(revs.mailmap);
 	read_mailmap(revs.mailmap);
 
 	if (prepare_revision_walk(&revs))
@@ -1122,7 +1122,6 @@ static const char *find_author_by_nickname(const char *name)
 		ctx.date_mode.type = DATE_NORMAL;
 		strbuf_release(&buf);
 		format_commit_message(commit, "%aN <%aE>", &buf, &ctx);
-		clear_mailmap(&mailmap);
 		release_revisions(&revs);
 		return strbuf_detach(&buf, NULL);
 	}